/*
 * Copyright (c) 2007 innoSysTec (R) GmbH, Germany. All rights reserved.
 * Original author: Edmund Wagner
 * Creation date: 31.05.2007
 *
 * Source: $HeadURL$
 * Last changed: $LastChangedDate$
 * 
 * the unrar licence applies to all junrar source and binary distributions 
 * you are not allowed to use this source to re-create the RAR compression algorithm
 * 
 * Here some html entities which can be used for escaping javadoc tags:
 * "&":  "&#038;" or "&amp;"
 * "<":  "&#060;" or "&lt;"
 * ">":  "&#062;" or "&gt;"
 * "@":  "&#064;" 
 */
package de.innosystec.unrar.unpack.ppm;

import java.io.IOException;

import de.innosystec.unrar.exception.RarException;
import de.innosystec.unrar.unpack.Unpack;

/**
 * DOCUMENT ME
 * 
 * @author $LastChangedBy$
 * @version $LastChangedRevision$
 */
public class RangeCoder {
	public static final int TOP = 1 << 24;

	public static final int BOT = 1 << 15;

	private static final long uintMask = 0xFFFFffffL;

	// uint low, code, range;
	private long low, code, range;

	private final SubRange subRange = new SubRange();

	private Unpack unpackRead;

	public SubRange getSubRange() {
		return subRange;
	}

	public void initDecoder(Unpack unpackRead) throws IOException, RarException {
		this.unpackRead = unpackRead;

		low = code = 0L;
		range = 0xFFFFffffL;
		for (int i = 0; i < 4; i++) {
			code = ((code << 8) | getChar()) & uintMask;
		}
	}

	public int getCurrentCount() {
		range = (range / subRange.getScale()) & uintMask;
		return (int) ((code - low) / (range));
	}

	public long getCurrentShiftCount(int SHIFT) {
		range = range >>> SHIFT;
		return ((code - low) / (range)) & uintMask;
	}

	public void decode() {
		low = (low + (range * subRange.getLowCount())) & uintMask;
		range = (range * (subRange.getHighCount() - subRange.getLowCount())) & uintMask;
	}

	private int getChar() throws IOException, RarException {
		return (unpackRead.getChar());
	}

	public void ariDecNormalize() throws IOException, RarException {
		// while ((low ^ (low + range)) < TOP || range < BOT && ((range = -low &
		// (BOT - 1)) != 0 ? true : true))
		// {
		// code = ((code << 8) | unpackRead.getChar()&0xff)&uintMask;
		// range = (range << 8)&uintMask;
		// low = (low << 8)&uintMask;
		// }

		// Rewrote for clarity
		boolean c2 = false;
		while ((low ^ (low + range)) < TOP || (c2 = range < BOT)) {
			if (c2) {
				range = (-low & (BOT - 1)) & uintMask;
				c2 = false;
			}
			code = ((code << 8) | getChar()) & uintMask;
			range = (range << 8) & uintMask;
			low = (low << 8) & uintMask;
		}
	}

	public static class SubRange {
		// uint LowCount, HighCount, scale;
		private long lowCount, highCount, scale;

		public long getHighCount() {
			return highCount;
		}

		public void setHighCount(long highCount) {
			this.highCount = highCount & uintMask;
		}

		public long getLowCount() {
			return lowCount & uintMask;
		}

		public void setLowCount(long lowCount) {
			this.lowCount = lowCount & uintMask;
		}

		public long getScale() {
			return scale;
		}

		public void setScale(long scale) {
			this.scale = scale & uintMask;
		}

		public void incScale(int dScale) {
			setScale(getScale() + dScale);
		}

	}
}
